State the three postulates of Bohr's theory of hydrogen atom.

Explanation

(i) An electron can not revolve round the nucleus in any arbitrary orbit . Only certain orbits are permitted . Electron does not radiate energy in stationary orbits.
(ii) The radius of the allowed electron orbits is determined by the quantum condition . It states that the orbital angular momentum of electron about the nucleus is an integral multiple of `h/(2pi)` . According to Bohr's postulate , `mvr=n((h)/(2pi))`
(iii) An atom radiates energy only when an electron jumps from a higher energy orbit to a lower energy orbit. If `E_(1) and E_(2)` are the lower and higher energies and v is the frequency of radiation then `v=((E_(2)-E_(1))/(h))`